Re: GTK/GDK equivalent to UpdateWindow() ?

[John Emmas <johne53 tiscali co uk>]

I've taken a quick look at gdk_window_flush() and gdk_window_process_updates() but they both require me to 
pass a pointer to GdkWindow.

My top level 'widget' is a Gnome::Canvas (essentially an enhancement of GktLayout, from what I can tell).  My 
"now line" is a Gnome::Canvas::Line which is derived from Gnome::Canvas::Item (I'm using gnomecanvasmm, of 
course).  However, these are all basically GTK widgets, I think.

But now comes the tricky bit....  according to Andrew Krause's book (Foundations of GTK+ Development) not all 
widgets have an associated GdkWindow.  They only acquire a GdkWindow if:-

a) They become "realized" (I assume this means "visible") - and;
b) If they're capable of responding to events.

I assume that my simple Gnome::Canvas::Line won't be able to respond to events - but the canvas itself will.  
Therefore, having hidden the line, I should be able to call gdk_window_flush() (on the canvas) which should 
force it to remove the now line.

But how/where do I acquire a pointer to the canvas's GdkWindow??